Starter device for an internal combustion engine for motor vehicles

Abstract: The device comprises a movable pinion (6) and a control electromagnet (3), a transmission comprising a rocker arm (8) being interposed between the core (10) of the electromagnet (3) and the pinion (6). In the portion in question of the drive appendage (15) turned towards the core (10), this arm (8) has a profile which is substantially perpendicular to the axis of translation of the core (10). The rocker arm (8) is produced by two coupled metal sheets.

Description: The present invention relates to a starter device for an internal combustion engine for a motor vehicle. More specifically, the invention relates to a starter device of the type comprising: a movable pinion which can mesh with a toothed wheel of the internal combustion engine; a control electromagnet comprising a core which can move between a rest position and an actuation position and has an end drive appendage; a transmission between the core of the electromagnet and the pinion, the transmission comprising a rocker arm of which the first end is coupled to a movable member controlling the translation of the pinion and a second end coupled with clearance to the appendage of the core of the electromagnet, such that, when the electromagnet is excited, the core leaves the rest position and travels through an initial dead stroke before the appendage causes the arm to pivot; and an electric motor which can be supplied so as to cause the pinion to rotate when the movable core of the electromagnet, having reached the actuation position, closes an electric switch. The transmission between the core of the electromagnet and the pinion is generally of non-rigid type. Actually the rocker arm is coupled with clearance to the drive appendage of the electromagnet. This clearance is provided so as to allow the movable core (which is in the actuation position ( with excited electromagnet)), when the electromagnet is de-energised, to travel over part of a stroke returning it to the rest position in which it is free from the thrust of the arm, such that the switch opens reliably and the motor is not supplied. As stated above, the transmission between the core of the electromagnet and the pinion is not rigid and may comprise one or more springs, provided, for example, so as to facilitate the meshing of the pinion and the toothed rim of the combustion engine if it is sticks at the front. Further, the rocker arm itself is frequently resiliently flexible. Because of the clearance in the rest position between the drive appendage of the electromagnet core and the rocker arm and to the fact that the transmission as a whole is not of rigid type, the movement of the pinion is not exactly proportional to that of the core. Therefore, when the core reaches the actuation position and the electric motor is supplied, it is not always ensured that the pinion meshes sufficiently with the toothed rim of the combustion engine. In order to overcome this disadvantage, European Patent Application No. EP-A-0 520 957 in the name of the same applicants, proposes producing the aforementioned rocker arm with a shaped profile such that, all other conditions being equal, the initial dead travel is less than it would be with an arm having a substantially straight profile. Typically, the second end of the rocker arm is deflected in correspondence with the core drive member or appendage. However, this solution has a disadvantage. In particular, this configuration can cause a deviation of the movable core of the electromagnet which, in the rest position can be subject to a non-axial reaction, owing to the thrust of the core return spring. As a result, the core is urged in a preferred direction. If these conditions should arise, the vibrations induced by the combustion engine will wear the movable core and the movable core guide at the points of contact. Since it is not uniformly distributed axially, this wear can cause the movable core to stick against its guide when the starter is driven, thus causing the starter to fail. In order to overcome this disadvantage, it is known to produce the second end of the rocker arm with an arcuate section in the area of contact with the movable core. However, this solution in part compromises the advantages obtained, deflecting the second end of the rocker arm towards the drive member. The object of the present invention is to produce a starter device which enables the above disadvantage to be overcome satisfactorily. According to the present invention, this object is achieved by a starter device having the characteristics indicated in the independent claim following the present description. Further advantages and characteristics will become clear from the following detailed description, given with the aid of the appended drawings, provided purely by way of non-limiting example and in which: Figure 1 is a schematic diagram, partially in section, of a device according to the present invention; Figure 2 is a schematic diagram of a component of the device according to the present invention; and Figure 3 is a diagram , in side view, of the component shown in Figure 2. With reference to Figure 1, the starter device for an internal combustion engine for motor vehicles comprises a support casing 1 which, in known arrangement, accommodates an electric drive motor 2 and an electromagnet 3. In the arrangement illustrated, an overrunning clutch (free wheel) 4 is mounted on the shaft of the electric motor 2. A sleeve 5 is mounted so as to move on the shaft of the motor 2 together with the joint 4. On the side opposite the motor 2, a pinion 6, which can move axially along a smooth end portion 2a of the shaft of the electric motor 2, is connected to the joint 4. The pinion 6 can in particular move between a retracted rest position and an advanced operating position in which it can mesh with the teeth of a flywheel 7 of the internal combustion engine (not illustrated). A rocker arm, pivoting about a fulcrum 9 and acting as a transmission member between the sleeve 5, which acts as a member for controlling the translation of the pinion 6, and the core of the electromagnet 3, is indicated 8. In the embodiment illustrated, the arm 8, which is substantially Y-shaped, is of the leaf spring type and comprises two coupled metal sheets, with a lower end 8a which engages in suitable seats arranged at the sides of the sleeve 5. The second end of the arm 8, indicated 8b, is coupled to the movable core 10 of the electromagnet 3, in a manner which will now be described. The electromagnet 3 comprises a movable core 10 which can move axially inside a control solenoid or winding 11 carried by a coil 12. At one end, the core 10 has an axial extension 13 about which a washer 14 is secured. The extension 13 of the core 10 terminates in an appendage 15 which has a slot 16 in which the second end 8b of the rocker arm 8 extends. A helical spring 17, which reacts against the washer 14, tends to maintain the core 10 in the position illustrated, in which it partially extends outside the control solenoid or winding 11, and in which the upper end 8b of the arm 8 rests against the righthand side (as observed in the drawing) of the slot 16. This end of the arm is thus at a given spacing from the lefthand side (as observed in the drawing) of the slot 16. According to the present invention, the arm 8 consists of two coupled metal sheets. However, at their second ends 8b, these two sheets are shaped differently with respect to the prior art described above. The half-lever which is furthest away from the core 10 is shaped similarly to that which has been described with reference to the prior art and is thus deflected in the direction of the drive member 15 of the core 10. In contrast, the half-lever positioned closer the core 10, shown in Figure 3, has an arcuate end portion with the concave part turned towards the core 10. This concavity can advantageously be dimensioned such that, when the arm 8 is in the rest position, the non-axial reaction with respect to the core 10 is zero. In this way, it is no longer possible for the disadvantage of the prior art to give rise to the aforementioned non-axial reaction. At the same time, the advantages resulting from the deflection of the second end 8b of the rocker arm 8 are maintained.

Claims: A starter device for an internal combustion engine for a motor vehicle, comprising: a movable pinion (6) which can mesh with a toothed rim (7) of the internal combustion engine; a control electromagnet (3) comprising a core (10) which can move between a rest position and an actuation position and comprises an end drive appendage (15); a transmission (8, 5) between the core (10) of the electromagnet (3) and the pinion (6); the transmission comprising a rocker arm (8) having a first end (8a) coupled to a movable member (5) which controls the translation of the pinion (6) and a second end (8b) coupled with clearance to the drive appendage (15) of the core (10) of the electromagnet, such that, when the electromagnet (3) is excited, the core (10) leaves the rest position and travels through an initial dead travel before this appendage (15) causes the arm (8) to pivot; and an electric motor (2) which can be supplied so as to cause the pinion (6) to rotate when the movable core (10) of the electromagnet (3), having reached the actuation position, closes an electric switch; the rocker arm (8) having a shaped profile such that the initial dead travel is less than it would be with an arm having a substantially straight profile, all other geometric conditions being equal; characterized in that the second end (8b) of the rocker arm (8) has a profile, in correspondence with the drive appendage (15) of the core (10) of the electromagnet (3), having a development which is substantially perpendicular to the axis of translation of the core (10) when the core (10) is in the rest position. A device according to Claim 1, characterized in that the profile which engages the drive appendage (15) and is turned towards the core (10) is substantially concave. A device according to Claim 1 or Claim 2, characterized in that the rocker arm (8) comprises two metal sheets, a first sheet being turned towards the drive appendage (15) and deflected, in correspondence with the second end (8b), towards the latter, and a second sheet turned towards the core (10) and having a profile which is substantially concave towards the core (10).

Inventors: CERIZZA GIOVANNI, FASOLA GIANCARLO, CERIZZA, GIOVANNI, FASOLA, GIANCARLO
Applicants: MAGNETI MARELLI SPA, INDUSTRIE MAGNETI MARELLI S.P.A.
Application year: 1994
Main classification: F02N15
IPC codes: F02N15